1. Field of the Invention:
The present invention relates to a starter for starting an engine.
2. Description of Related Art:
Both a biaxial-type starter and a coaxial-type starter are known, for instance, by Laid-Open Japanese Utility Model Publication No. 6-43979 and Laid-Open Japanese Utility Model Publication No. 1-130071.
In the coaxial-type starter, an electromagnetic switch is positioned outward from an output shaft of a starter, a rotation shaft of an armature, in the radial direction thereof so that the electromagnetic switch is coaxial with the output shaft. This construction prevents the electromagnetic switch from projecting outward from the starting motor in the radial direction thereof. Therefore, electromagnetic switch of the coaxial-type starter can be installed on a car more easily than the biaxial starter.
In the coaxial-type starter, however, the distance between the electromagnetic switch and the starting motor in the axial direction of the rotation shaft is long and further, a commutator is provided at the side opposite to the side in which the output shaft of the starting motor is positioned. Thus, the wire connection construction for electrically connecting a fixed contact of the electromagnetic switch and the brush positioned on the commutator with each other is complicated, thus necessitating an increased number of installing processes to be performed. Moreover, the wire connecting the fixed contact and the brush with each other is long, thus causing the electric resistance of the wire to be large and hence degrading the output of the starter.
In the coaxial-type starter, the outer diameter of a plunger of the electromagnetic switch is large, which increases the diameter of the spool of an excitation coil. Consequently, the amount of copper of the excitation coil wound on the spool increases, which increases the weight of the starter.
Further, the plunger is cylindrical and therefore there is a possibility that the plunger is rotated under the influence of the vibration of the engine and that a sleeve provided inside the spool and other sliding-contact portions in the periphery of the plunger are worn.
Further, a battery terminal and a switch terminal project in the same direction in the radial direction of the electromagnetic switch and are proximate to each other. Thus, wires can be connected readily with the battery terminal and the switch terminal. However, the battery terminal and the switch terminal are so close to each other that wires interfere with each other and tools. The operation of installing the battery terminal and the switch terminal on the housing cannot be performed with ease.
It is therefore a first object of the present invention to provide a starter in which a wire connection between an electromagnetic switch and a brush can be accomplished readily.
It is a second object of the present invention to provide a starter having a construction which does not prevent the layout of an engine from being restricted and allows the use of a possible least amount of copper for use in a coil of an electromagnetic switch.
It is a third object of the present invention to provide a starter having a construction which prevents the rotation of a plunger against the vibration of an engine, thus restraining a peripheral part of the plunger from being worn.
It is a fourth object of the present invention to provide a starter having a construction which facilitates an operation of wiring a battery terminal and a switch terminal and installing them on a housing.
According to a first aspect of the present invention, an electromagnetic switch is positioned radially outwardly from a peripheral surface of a rotation shaft in an axial range between a commutator and an epicycle reduction gear and is coaxial with a rotation shaft, the distance between a brush which slides in contact with a commutator and the electromagnetic switch is made axially short. This construction facilitates the connection between a motor-side fixed contact and a positive brush and further, a wire connecting the motor-side fixed contact and the positive brush with each other is made short. Accordingly, the resistance of the wire is made small and the output of the starter can be improved.
According to a second aspect of the present invention, the axis of an electromagnetic switch substantially parallel with an output shaft is positioned inward from the peripheral surface of a starting motor in the radial direction of the output shaft. This construction restrains the peripheral part of a plunger from being worn because the rotation of the plunger is prevented and in addition, reduces the projection amount of the electromagnetic switch in the radial outward direction thereof. Further, a small amount of copper can be used for the attraction coil.
According to a third aspect of the present invention, the sectional shape of an electromagnetic switch perpendicular to the axis there of is flat in the radial direction of a starter. The projection amount of the electromagnetic switch can be reduced because it is flat in the radial direction of the starter compared with the case in which the electromagnetic switch is circular in the sectional shape. Moreover, the rotation of a plunger can be prevented against the vibration of an engine. Thus, the peripheral part of the plunger can be prevented from being worn.
According to a fourth aspect of the present invention, a battery terminal and a switch terminal project in the substantially same direction in the radial direction of an electromagnetic switch, so that they can be installed on the housing in the same direction and wires can be connected with the battery terminal and the switch terminal easily. Further, the wires connected therewith can be prevented from interfering with each other, and tools and the wires can be also prevented from interfering with each other, although they project in the same direction and proximate to each other. The battery terminal and the switch terminal are axially spaced at an appropriate interval from each other.